[Feeding ecology of Chaeturichthys stigmatias during autumn in Haizhou Bay]. / 海州湾秋季矛尾虾虎鱼的摄食生态.

Research about feeding ecology of fish is important to understand individual behavior and population development, which is also the basic to analyze trophic structure and function of aquatic ecosystems. Chaetrichthys stigmatias is one of the key species in the Haizhou Bay fisheries ecosystem, which has critical ecological niche within the food web. In this study, we collected samples through bottom trawl surveys during the fall of 2018 in the Haizhou Bay, and analyzed the feeding ecology of C. stigmatias based on both stomach content analysis and stable isotope technology. The results showed that the primary diet groups for C. stigmatias were Ophiuroidea and Shrimp, including Ophiothrix marenzelleri, Ophiopholis mirabilis, Ophiura sarsii, Penaeidae, and Alpheus japonicus. The range of δ13C values of C. stigmatias was from -19.39‰ to -15.74‰, with an average value of (-18.07±0.87)‰, which had no significant correlation with body length. The range of δ15N values was from 8.16‰ to 12.86‰, with an average value of (10.14±1.51)‰, which was positively correlated with body length. The trophic level of C. stigmatias showed a positive relationship with body length, with an average value of (3.74±0.34) and a range value of 3.32 to 4.20 among different size groups. The contribution rates of different prey groups varied significantly. Based on the structural equation modeling, we found that the feeding intensity of C. stigmatias was primally influenced by body length, sea bottom salinity, sea bottom temperature, and water depth, with a particularly signi-ficant positive correlation with body length. The combination of stable isotope technology and stomach content analysis methods could contribute to comprehensive understanding on the feeding ecology of C. stigmatias, providing essential data and foundation for research on trophic structures and resource conservation in the Haizhou Bay ecosystem.

Influencing factors of predation on five keystone prey species in Haizhou Bay based on Delta-GAMMs.

Trophic dynamics is one of the major regulators of fishery production in marine ecosystems, which is important for the implementation of ecosystem-based fisheries management. Based on data collected form bottom trawl surveys in Haizhou Bay and adjacent waters during autumn of 2011 and 2018, Delta-GAMMs (Delta-generalized additive mixed models) were constructed to evaluate the effects of biotic and abiotic factors on the predation of five key prey species (including Leptochela gracilis, Alpheus japonicus, Loligo spp., Larimichthys polyactis, and Oratosquilla oratoria) in the Haizhou Bay. Percent frequency of occurrence and predation pressure index were used to identify their major predators. Variance inflation factor and full subsets regression were analyzed to quantify the degree of multicollinearity between these factors. The results showed that the occurrence frequency of keystone prey species in the stomach of predators ranged from 8.5% to 42.2%, and the weight percentage ranged from 4.2% to 40.9%. The average deviance explanation rate of the "binomial" model was 16.1%, and the average deviance explanation rate of the "positive" model was 23.8%. Body length of predator, predator population density, and sea bottom temperature were important factors influencing prey-predator trophic interactions. Predator length was the most important factor, with feeding probability and weight percentage of keystone prey species all increasing with body length of predator. Feeding probability and weight percentage of key prey species decreased with predator population density. The effects of environmental factors such as sea bottom temperature, depth of water, latitude, and sea bottom salinity showed different trends, depending on the prey-predator assemblage. This study showed that the Delta-GAMMs was an effective method to explore the trophic interactions between prey and predators in marine ecosystems, and could provide a theoretical basis for the conservation and sustainable use of fisheries resources.

Species composition and spatial and temporal distribution of occasional fishes in Haizhou Bay, Shandong, China.

Occasional species are often neglected in community ecology studies due to low abundance and frequence. However, they are closely related to biodiversity maintenance and marine conservation. We used index of relative importance (IRI), distribution center of gravity and Mann-Kendall trend test to elucidate the spatial and temporal distributions and changing trends of occasional fishes in Haizhou Bay based on the fishery resources survey data collected from 2013 to 2019. The occasional fishes in Haizhou Bay was identified based on IRI. Nine of the occasional species were selected to analyze the spatial distribution and interannual trends of relative biomass and occurrence frequency. The results showed that a total of 93 fish species were recorded in the multi-year survey in Haizhou Bay. Among which, 61 species had IRI<10, indicating the existence of a large number of occasional fishes in Haizhou Bay. The nine selected occasional species had distinctive spatial distribution characteristics. Erisphex pottii, Azuma emmnion, and Raja porosa were mainly distributed in the eastern part of Haizhou Bay, with a wide habitat range. Sphyraena pinguis, Coilia nasus, and Zebrias zebra were distributed in the western and southern parts, respectively. The rest species were mainly distributed in the southwestern part. In terms of interannual variation, the biomass and occurrence frequency of Coilia mystus, R. porosa, A. emmnion, and S. pinguis showed fluctuating changes, while Odontamblyopus rubicundus and Ctenotrypauchen microcephalus showed an increasing trend. The biomass and occurrence of Z. zebra, C. nasus and E. pottii gradually decreased with no catch in recent years. This study would contribute to the understanding of the spatial and temporal distribution of occasional species, and provide guidance for the conservation of occasional biological resources and species diversity, especially for the establishment of marine protected areas.

[Feeding ecology of Amblychaeturichthys hexanema in Haizhou Bay based on linear mixed model]. / åŸºäºŽçº¿æ€§æ··åˆæ¨¡åž‹ç ”ç©¶æµ·å·žæ¹¾å ­ä¸é’å°¾è™¾è™Žé±¼æ‘„é£Ÿç”Ÿæ€.

Many traditional economic marine fishery resources have been declining in the coastal waters of China. Amblychaeturichthys hexanema has become one of the dominant species in Haizhou Bay and some other coastal areas of China, playing an important role in marine food webs. We analyzed the feeding strategy of A. hexanema based on the bottom trawl surveys conducted in the Haizhou Bay and adjacent waters in spring and autumn of 2011 and 2013-2016. The feeding habits and main influencing factors of A. hexanema were studied using linear mixed model (LMM). The results showed that A. hexanema fed on 14 prey groups, with Amphipoda, shrimps, Bivalvia and Ophiuroidea as the main prey groups. A total of 37 species were identified in the preys. The dominant prey species were Gammarus sp., Leptochela gracilis, Monoculodes sp., Moerella iridescens and Alpheus distinguendus. Results of the linear mixed model showed that the feeding intensity of A. hexanema in Haizhou Bay was influenced by body length, water depth, survey season, and bottom water salinity. Among them, water depth and bottom salinity had significantly negative effects, whereas the impact of body length was significantly positive. The feeding intensity was significantly higher in spring than that in autumn. Results of cluster analysis showed that A. hexanema had different feeding habits between two length groups as divided by a threshold of 70 mm body length. The change of feeding habit was mainly attributed to the variations in predation ability and food availability. Feeding strategy analysis showed that trophic niche of A. hexanema had large components between phenotypes and low intraspecific competition for prey. This study would contribute to our understanding of life history characteristics and ecological habits of A. hexanema, and provide scientific support for the sustainable utilization and management.

[Spatio-temporal variations in species composition and diversity of fish communities in the adjacent waters of Changshan Islands, China]. / é•¿å±±åˆ—å²›é‚»è¿‘æµ·åŸŸé±¼ç±»ç¾¤è½ç§ç±»ç»„æˆå’Œå¤šæ ·æ€§æ—¶ç©ºå˜åŒ–.

In order to understand species composition and diversity of fish communities in the ecotone between the Yellow Sea and Bohai Sea, we examined species composition and temporal and spatial variations of fish species diversity using the relative importance index (IRI), species diversity index and k dominance curve based on bottom trawl survey data of fish resources in the adjacent waters of the Changshan Islands in October 2016, January, May and August 2017. The results showed that 77 fish species were captured, mainly temperate water fishes, demersal fishes and migratory fishes. The dominant species exhibited obvious seasonal variation. The dominant species in spring and winter were Lophius litulon, and those in summer were pelagic species such as Scomber japonicus and Engraulis japonicus. A total of 46 migratory fish species were found throughout the year. The seasonal species migration indices were all higher than 100, while the species migration index was the largest in autumn. The species diversity index showed high spatial and temporal dynamics, with the highest species richness in spring and the highest Shannon diversity and evenness in autumn. There was a significant negative correlation between species richness and sea surface temperature in summer, significant positive correlations between species richness and depth and bottom temperature in winter, and a significant positive correlation between Shannon diversity index and sea bottom temperature. In short, fish community showed high species diversity, rich migratory species and obvious temporal and spatial heterogeneity in the adjacent waters of the Changshan Islands, which is an ecotone between the Yellow Sea and the Bohai Sea.

[Habitat characteristics of Octopus ocellatus and their relationship with environmental factors during spring in Haizhou Bay, China]. / æµ·å·žæ¹¾æ˜¥å­£çŸ­è›¸çš„æ –æ¯åˆ†å¸ƒç‰¹å¾åŠå ¶ä¸ŽçŽ¯å¢ƒå› å­çš„å ³ç³».

In recent years, a variety of important fishery resources in China's coastal waters have declined. Octopus ocellatus has the characteristics of short life cycle and rapid growth, with great contributions to fisheries of China's coastal waters. However, we know little about the habitat distribution characteristics of O. ocellatus and its relationship with environmental factors, which is not conducive to better protection and utilization of its resources. Here, we analyzed the distribution characteristics of O. ocellatus and its relationship with environmental factors using three machine learning methods, i.e., random forest model, artificial neural network model, and generalized boosted regression models, based on the survey data of fishery resources and habitat in Haizhou Bay during spring of 2011 and 2013-2017. Among the three models, random forest model had great advantages in the fitting effect and prediction ability. The model analysis results showed that sea bottom temperature, seawater depth and sea bottom salinity had significant effects on the habitat distribution of O. ocellatus. The relative resource density of O. octopus increased first and then decreased with the increases of sea bottom temperature, seawater depth, and sea bottom salinity. Based on environmental data simulated by the FVCOM model, we predicted the habitat distribution of O. ocellatus in Haizhou Bay using random forest model and found that O. ocellatus was mainly distributed in the area between 34.5°-35.8° N and 119.7°-121° E.

[Sampling design optimization based on estimation accuracy and survey cost for fishery-independent surveys]. / åŸºäºŽä¼°è®¡å‡†åº¦å’Œè°ƒæŸ¥è´¹ç”¨çš„æ¸”ä¸šèµ„æºè°ƒæŸ¥é‡‡æ ·è®¾è®¡ä¼˜åŒ–.

Optimization of sampling design can reduce survey cost, ensure the accuracy of survey data, and get the maximum benefit of survey design. In this study, survey voyage was added into sampling survey design optimization as the evaluation index to quantify the survey cost. Computer simulation and resampling technique were used to simulate the survey plan. Simulation annealing algorithm was used to find the survey design with the shortest voyage. Based on the survey data collected from the bottom trawl survey conducted in the Haizhou Bay and its adjacent waters in spring and autumn from 2013 to 2015, Kriging interpolation was used to simulate the relative abundance distribution of Conger myriaster, Enedrias fangi, and Hexagrammos otakii in the bay in two seasons as their 'true' values. Resampling was conducted using stratified random sampling with different sample sizes for simulation study, and the abundance indices of each target species were estimated based on the simulated data. The relative bias (RB) was used to evaluate the accuracy of estimation of abundance index. The average survey cost and probability of budget overshoot (P) were used to measure the cost of survey. Integrated evaluation index (IEI) was developed to measure the survey cost and estimation accuracy comprehensively. The results showed RB values of all target species decreased with sample size. Different target species had different RB values with the same sample size. The optimal numbers of station determined by different evaluation indices were different. The optimal sample size determined by RB was relatively high, while the cost exceeded the budget of survey. The optimal sample size determined by probability of exceeding survey budget was relatively low but the accuracy and precision of estimation was low. IEI balanced the survey cost and estimation accuracy, and the optimal sample size defined by IEI was at intermediate level. The sampling design considering survey cost and route planning could not only determine the optimal sample size, but also record the potential station location, the survey sequence and the corresponding survey cost of simulations. According to the actual cost budget, the desired survey design with low cost and low RB of estimation from simulations could be chosen for fishery-independent surveys.

Understanding the feeding ecology of Cynoglossus joyneri in Haizhou Bay based on stable isotope analysis.

We analyzed the feeding ecology of Cynoglossus joyneri by carbon and nitrogen stable isotope analysis based on the samples collected from the bottom trawl surveys during spring and autumn of 2018 in Haizhou Bay, China. The results showed that the δ13C and δ15N values of C. joyneri ranged from -20.75‰ to -15.91‰ and from 5.98‰ to 12.02‰, respectively. The mean values of the δ13C and δ15N were (-17.79±1.00)‰ and (9.37±1.33)‰, respectively. There was a significantly negative correlation between the δ13C values and standard length and a positive correlation between the δ15N values and standard length. The mean trophic level of C. joyneri was (3.43±0.97). There was a significantly positive correlation between the trophic level and standard length. The dominant prey groups of C. joyneri were fish, crabs, shrimps, mollusca, polychaeta, plankton and particle organic matter (POM). The trophic contribution of shrimps was the highest among these prey groups. The trophic contribution of fish, crabs and shrimps was higher in autumn than those in spring. This study would help to understand the role of C. joyneri in the material cycling and energy flow in Haizhou Bay ecosystem, and provide scientific basis for the protection and rational utilization of this species.

[Identification of keystone predators in Haizhou Bay food web based on the revised SURF index]. / 基于改进的SURFæŒ‡æ•°ç”„é€‰æµ·å·žæ¹¾é±¼ç±»ç¾¤è½çš„å ³é”®æ•é£Ÿè€ .

Keystone predator species play an important role in regulating the number, richness and distribution of prey species. Based on the bottom trawl surveys in Haizhou Bay, keystone predator species in fish communities were identified by the revised SURF (supportive role to fishery ecosystems) index. Conger myriaster, Saurida elongata, Hexagrammos otakii, Chelidonichthys spinosus, and Larimichthys polyactis were the keystone predators in the fish community. They had high number of nodes degree, and were also the main predators of many species. Further, they had strong ability of clustering. The fluctuations of their density would have great impacts on ecosystem energy flow and food web structure. The method not only considered the feeding ratio between species, but also took the amount of catch and abundance of species as important factors in the identification of keystone predators. Compared with the traditional method, this method had great improvement and provided a new one for the identification of key predators. Our results showed that the strong inter-specific interactions played an important role in maintaining the structure and function of food webs. Protection of key predators would benefit the stability of biological communities and species diversity. Therefore, ecosystem-based fisheries management (EBFM) should give priority to the protection of key species. The important economic fish species, C. myriaster and L. polyactis, should be protected with high priority as they suffered from higher fishing pressure.

[Interspecific association of main fish species in the Haizhou Bay and its adjacent waters]. / æµ·å·žæ¹¾åŠå ¶é‚»è¿‘æ°´åŸŸä¸»è¦é±¼ç±»ç§é—´å ³è”æ€§.

It is important to reveal the interspecific association and correlation of main species for deep understanding of fish community structure and function. Based on data collected from the bottom trawl surveys from 2013 to 2017 in the Haizhou Bay and the adjacent waters, we analyzed interspecific association of main species using Chi-square test, Jaccard index, and Spearman rank correlation coefficient. There were consistent results from χ2-test, Jaccard index, and Spearman's rank correlation analysis. The proportion of positively correlated species pairs was high in different years, whereas the number of significant or extremely significant species pairs was low. There were 9, 6, 7, 1, 0 significant or extremely significant species pairs over different years based on Jaccard index. There were 12, 20, 13, 5, 6 significant or extremely significant species pairs over different years based on Spearman's rank correlation coefficient. While there were inter-annual changes in related species pairs, the relationship between significant species pairs was relatively stable, indicating a relatively stable interspecific association in the main fish communities. The species within the same ecological type could replace each other in the niche, which have adapted to environmental changes in Haizhou Bay and its adjacent waters.

[Feeding habits of Saurida elongata in Haizhou Bay, Shandong, China, based on stomach contents and stable isotope.] / åŸºäºŽèƒƒå«ç‰©å’Œç¨³å®šåŒä½ç´ ç ”ç©¶æµ·å·žæ¹¾é•¿è›‡é²»çš„æ‘„é£Ÿä¹ æ€§.

Saurida elongata, a warm-water offshore benthic fish, is one of the dominant species in Haizhou Bay and plays an important role in the food web. Based on samples collected from bottom trawl surveys in Haizhou Bay, we examined the feeding habits of Saurida elongata based on both stomach content and stable isotope analyses. The results showed that the main prey species of Saurida elongata were Metapenaeopsis dalei, Loligo spp., Cryptocentrus filifer, Engraulis japonicus, Chaeturichthys hexanema, Apogonichthys lineatus, Syngnathus acus and Callionymus beniteguri. The range of δ13C value was -19.39‰ to -16.23‰, with an average value of (-18.01±0.85)‰. There was no correlation between body length and δ13C values. The value of δ15N ranged from 9.56‰ to 13.36‰, with an average value of (11.77±0.86)‰, which was significantly positively correlated with body length. There was substantial difference in the contribution of food organism among diffe-rent body length groups. With the increases of body size, predation ability and morphology of feeding organs gradually improved, and the proportion of prey organisms changed, which might be the main reason for the ontogenetic variation in feeding habits. This study could contribute to understand the feeding ecology of snake mullet in Haizhou Bay and provide basic information for the nutritional dynamics of the Haizhou Bay food web.

[Spatio-temporal variations of functional diversity of fish communities in Haizhou Bay.] / æµ·å·žæ¹¾é±¼ç±»ç¾¤è½åŠŸèƒ½å¤šæ ·æ€§çš„æ—¶ç©ºå˜åŒ–.

As the link among species, ecological environment, and ecosystem function, functional diversity can help us to better understand the relationship between biodiversity and ecosystem function. We analyzed functional diversity with thirteen functional traits reflecting the characteristics of food acquisition, locomotion, ecological adaptation, reproduction and population dynamics of fish species. The seasonal, interannual and spatial variations of functional diversity of fish communities were examined using functional richness index (FRic), functional evenness index (FEve), functional divergence index (FDiv) and community weighted mean index (CWM) based on the data from the bottom trawl surveys in spring and autumn from 2011 to 2017 (except 2012) in Haizhou Bay. The results showed that functional diversity indices were significantly different in spring and autumn, with FRic was significantly higher in autumn than that in spring and FDiv was significantly higher in spring than that in autumn. Migration might be the main reason for the seasonal change of functional diversity indices. CWM analysis showed that dominant fish species were cold-temperate or warm-temperate species, with higher trophic level, strong motion ability, and relatively high growth coefficient, resilience and vulnerability in spring. In autumn, the dominant species showed the opposite traits. In both spring and autumn, fish species with pelagic eggs dominated the fish communities. Inter-annual variations in functional diversity indices were observed in spring and autumn. The functional diversity indices showed an annual fluctuation during the study period in both spring and autumn, indicating the low stability of fish community in Haizhou Bay. Significant spatial changes in functional diversity of fish assemblages were observed, with FDiv being higher in the offshore coastal waters (>20 m) than that in the shallow waters (<20 m). The functional diversity showed obvious spatio-temporal variation. The ecological niches and resource utilization of fish species varied with season, year and space in Haizhou Bay.

[Variations in the mean trophic level and large fish index of fish community in Haizhou Bay, China]. / æµ·å·žæ¹¾é±¼ç±»ç¾¤è½å¹³å‡è¥å »çº§å’Œå¤§åž‹é±¼ç±»æŒ‡æ•°çš„å˜åŒ–ç‰¹å¾.

Based on the bottom trawl surveys in spring (May) and in autumn (September to October) from 2011 to 2017 (except 2012) in Haizhou Bay, variations in the mean trophic levels (MTL) and large fish index (LFI) of fish community were examined to understand the changes of fish community structure in Haizhou Bay. The results showed that the dominant fish species were Hexagrammos otakii, Enedrias fangi, Syngnathus acus, Pseudosciaena polyactis and Saurida elongata, which had obvious seasonal variation. The mean trophic level of fish community varied significantly among different years and seasons. Generally, MTL in autumn was higher than that in spring, and the variation of which in autumn always lagged behind that in spring. The result of LFI calculation showed that the large fish resources declined and fish community structure in Haizhou Bay showed an obvious tendency of miniaturization in recent years.

[Interannual changes in fish community structure in the northern part of the coastal waters of Jiangsu Province, China in spring.] / 江苏近海北部海域春季鱼类群落结构的年间变化.

Based on the data collected from the bottom trawl surveys in the coastal waters of northern Jiangsu Province from 2009 to 2014, multivariate statistical analysis and other integrated indices were used to analyze the variation in the community structure of fish assemblage over time in the waters. The results showed that 68 species had been caught in the coastal waters of northern Jiangsu Province. There were significant fluctuations in the relative density of fish resources. The mean catch mass per site ranged from 0.75 to 1.62 kg·h-1, and the mean catch individuals per site showed significant decrease in the survey period ranging from 370 to 203 ind·h-1. The mean trophic level (MTL) index varied between 3.58 and 3.72 from 2011 to 2014, being relatively low in 2009-2012 and fluctuating around 3.70 in 2011-2014. The mean body mass of fish community increased from 2.93 to 11.18 g between 2009 and 2014, showing a similar tendency with that of MTL index. Cluster analysis and MDS showed that the six survey years could be divided into two subgroups of 2009-2010 and 2011-2014. The main discriminating species were Syngnathus acus,Ctenotrypauchen microcephalus and Ammodytes personatus for the two subgroups. Further study showed that the pelagic and planktivorous fishes had gradually increased in dominance while cold temperate species and indigenous species had decreased over the years. It was suggested that fish communities in the coastal waters of northern Jiangsu Province underwent a remarkable succession. Advices for the fisheries management in the waters were provided according to the succession pattern, which might contribute to the sustainable utilization of fishery resources.

[Macrozoobenthos functional groups in intertidal flat of northwest Jiaozhou Bay].

Based on the survey of macrozoobenthos at 35 locations of 7 sections in the intertidal flat of northwest Jiaozhou Bay in February, May, August, and November 2009, three zones including high tidal zone (A), mid tidal zone (B, C, and D), and low tidal zone (E) were selected to study the functional groups of macrozoobenthos in the flat. A total of 71 macrozoobenthos species were recorded, most of which were of mollusk (31 species), polychaete (20 species), and crustacean (14 species). The species number in A, B, C, D, and E was 26, 33, 35, 38, and 31, respectively. According to their food preferences, the macrozoobenthos were classified into 4 functional groups, i. e., planktonphagous, carnivorous, omnivorous, and detritivorous. The percentage of the species number of each functional group in the total species number of macrozoobenthos was in the order of carnivorous > planktophagous > detritivorous > omnivorous. Carnivorous group had the highest species diversity index, while omnivorous group had the lowest one. Overall, the species richness index, evenness index, and species diversity index were higher in mid tidal zone and lower in high and low tidal zones. The present study showed that the distribution of macrozoobenthos functional groups varied with the environment of tidal zones, being an integrative reflection of their habitat conditions.